Broad band variable tuning coil



1948- sfix. WEISS 2,453,477

BROAD BAND VARIABLE TUNING COIL Filed July 27, 1944 2 Sheets-Sheet 1 INVIIINTOR Ski/ kg [rang Wezss Jam WM ATTORNEY S 44- I38 Nov. 9, 1948. s. l. WEISS BROAD BAND VARIABLE TUNING COIL 2 Sheets-Sheet 2 Filed July 27, 1944 INVENTOR 62 16 15 ATTO R NEYS Patented Nov. 9, 1948 UNITED STATES PATENT OFFICE 8 Claims. 1

The present invention is concerned with inductor units and with circuits incorporating the same.

It is among the objects of the invention to provide a simple, rugged, self-contained inductor unit, which with but a single coil permits tuning over a broad band of frequencies with a minimum of loss and also permits matching practically any effective load impedance into or out of said coil at any frequency within said broad range.

According to the invention in a preferred embodiment, the inductor coil is mounted on a hollow insulating form, carrier or drum rotatable on gudgeons between which said coil is electrically connected. Taps from the coil, within the hollow drum are connected to collector rings also about the drum. Contact shoes mounted on metal rods ride upon these rings to which they are keyed. A separate contact shoe similarly keyed to a similar rod rides upon the inductor coil along the length of which it moves as the drum is turned, for including the desired number of turns on said. coil in the impedance load, for matching or dissipating power generated.

In the accompanying drawings in which is shown one of various possible embodiments of the several features of the invention,

Fig. 1 is a diagrammatic view of a circuit showing a preferred application of the invention,

Fig. 2 is a side elevation of the unit,

Fig. 3 is a top plan view of the unit as shown in Fig. 2,

Fig. 4 is a bottom plan view of the unit as shown in Fig. 2,

Fig. 5 is a transverse sectional view taken on line 5-5 of Fig. 2,

Fig. 6 is a transverse sectional view taken on line 66 of Fig. 2,

Fig, 7 is a detail sectional view on a larger scale taken on line 1--'I of Fig. 2, and

Fig. 8 is a detail sectional view on line 8-8 of Fig. 2.

Referring now to the diagrammatic view of Fig. 1, there is shown a more or less conventional tank circuit such as the final stage in a broadcasting circuit, and an associated impedance load, such as the antenna. Illustratively, the plate Ill of the valve V is connected by lead H to the inductor coil C which is grounded through lead 12. A variable condenser I3 is connected across the leads H and i2 and als across the inductor coil C. The latter, according to the present invention, has taps t1 and t2 connected respectively to rings 1'1 and r2 which may be rotatable with the inductor unit, said rings being connected by contact shoes s1 and $2 to switch contacts l4 and I5 respectively, adapted to be bridged by switch disk It, a third switch contact I! being connected to ground. Upon the coil C rides contact shoe I mounted on a metal rod I8 connected to the variable impedance load, such as antenna I9, a succeeding stage of amplification or other load.

In the setting of switch l5, shown in Fig.1,

the entire length of the inductor coil C is in circuit. The lower section of the coil is shortcircuited and only the section a is in circuit when the switch l6 bridges across contacts l1 and it, while in the third position in which the switch disk bridges across all three contacts IT, M and [5 only the shortest section b of the coil is in circuit. Thus depending upon the position of the switch, the inductor may be set for various ranges of frequency, corresponding to the number of turns of the inductor coil that are in circuit.

The same inductor coil C serves also for matching to the antennae or succeeding stage; for, depending upon the position of contact shoe 1 any selected number of turns of the coil C, i. c. all the turns below the contact shoe 1 as shown in Fig. 1 are in the load circuit, so that the frequency of the latter may be adjusted, readily to match that of the tank circuit.

By the arrangement of circuit shown, the present invention thus dispenses with the need for a distinct inductor coil for each frequency range, as well as for separate tuning facilities for the antennae or other load. The single inductor coil serves for both purposes.

In Figs. 2 to 8 inclusive, is shown a practical form of inductor coil unit according to the present invention, useful in the general type of circuit shown in Fig. 1. In a preferred embodiment'th'e unit is self-contained and involves a separate frame for carrying the inductor coil C. That coil is desirably of uncovered round wire mounted upon a hollow cylindrical form, carrier or drum, 20 of suitable insulating material, preferably of ceramic. For equal spacing of the coil convolutions upon the drum 20, the surface of the drum has a helical groove 2!, firmly accommodating the wire, the crown of which protrudes therefrom in the manner of a helical track.

Insulating disks 22 plug the respective ends of the drum, and each disk carriesa gudgeon or stub shaft 23, 24 respectively, affixed thereto as by collar 25 at one end and nut 26 at the other. Each end of the coil C extends through a corresponding aperture 2'! in the drum and is con formed as an eye 28 therein into which one end of a wire 29 is soldered, said wire leading to the nut 26 on the gudgeon to which its other end is soldered at 29. i

The gudgeons 23 and 24 are mounted in bearings on insulating end plates 30 and 3| respec' tively. Said end plates are conformed into a frame by means of intervening metal; spacer rods 39, 40 and 4|, the ends of'which are afiixed to said plates. Each gudgeon extends through a spherical mount 34 in a corresponding aperture 35 in the end plate, and is engaged by the edge portion 36of metal bearing plates 36. v Thus.

ready accommodation is afforded in case of inaccuracy in the drum. By means oi leaf spring 25' interposed between collar .25 and the inner plate 35,, electrical connection assured through the mounting bolts 12 to the outer plate at each end plate, Binding post ill at one conmeets to lead II, and binding post H connects at the other end. by means of strap 12 to grounding terminal 13.

Upon the drum there are also a plurality, illustratively two collector rings 21 and in, also of uncovered wire, desirably the same type of wire as is used for the inductor coil and also located in and rising from corresponding grooves 42 in the drum. The ends of the wire making up each collector ring extend through .an aperture l3 (Fig. 7) in the hollow drum and are formed into eyes 36 on the inside of the drum, the apertures being fill-ed by solder. A connector wire 45 along the inside of the drum is soldered into one of the .eyes 44 atone end and connected to a correspondins place on the inductor coil at the other end. For that purpose a stud 4t is passed from the interior outward through .a radial aperture in the drum and its narrowed outer end 4'! abuts the corresponding part of an inductor wire convolution and is brazed thereto. The inner end of said stud has a transverse aperture it through which the other end of the connector t? extends and into which it is brazed. Desirably connector 45 extends longitudinally of the drum as shown, collector ring r1 being connected to the inductor wire at point 4.9 and collector ring 122 being con nected to the inductor wire at point 50.

Electrical connection is made from each collector ring Ti and T2 to a corresponding terminal on the end plate 30. For this purpose, contact shoes, desirably rollers .91 and s2 are used, each .of which presents a peripheral groove 9 straddling the crown of the corresponding collector ring. Shoe s1 is mounted upon a metal rod 54 afiixed at its ends in the respective end plates 35: and 3! electrically connects to binding post .55 on end plate 30. Similarly, collector ring r2 has an associated shoe or roller 52 connected by its carrier rod 152 to a binding post 53. also on end plate (ill.

Parallel to end plate 3.0 there is preferably mounted aswitch plate 5-5. This plate may, if desired, be aflixed upon the ends of the spacer rods 3.9, MI which protrude beyond plate for that purpose and have spacing collars 5.! thereabout intervening between the end plates and the switch plate, the latter being affixed by nuts :58 threaded upon the ends of said rod. The switch plate carries three sets 01 spring contact jaws ll, 14 and IS with which the switch disk l6 coacts. Contact :14 is connected to binding post 53 by con necting wire 16!) and contact '55 to binding post 55 by connector wire 5!. The third contact H is connected by wire 62 to grounding terminal 63. li he switch is desirably operated by lever 64 be-- tween the switch plate 56 and the end plate '30.

Upon the inductor coil there also rests a con tact shoe 2 desirably a roller similar to roller 51 which is suitably mounted upon a metal rod 85 mounted at its ends to the end plates 30 and 3!. Rod 55 has brazed thereto a pair of transverse spring blades 66 which press upon insulating rollers 61 desirably of styrene upon the ends of the spacer rods '39, 40.

It "will'be seen that upon rotation of the drum, the roller 1 will be propelled by the helical wire C to the crown of which it is keyed at groove g to rotate and move longitudinally of the rod 65,

ing its knob 64' for the desired range of tin o 4 so as to engage the inductor coil at any selected portion of the length thereof.

The drum .0 may be rotated by any suitable means. The arran ement illustratl. sly shown in the drawings involves an operating knob 88 upon the end of a shaft 59 rotating in a metal block TE] affixed to the end plate fit and carrying a beveled gear "It at its end as shown in Fig. 2, meshing with .a co-acting bevel gear it upon the end of the gudgeon 23.

To prevent the shoe I from riding on either end of the coil C, end stop studs are mounted in the wall of the drum as for instance by means of nuts 71, each stud having a fiat stop blade it that engages the correspondin shoes "-d blocks its further advance when the shoe approaches the extremity of the coil.

It will be understood that the or other inductive load will be soldered to the end of one of the spring blades connected to the rod The device has mounting lugs or bras l3 at the end of the end plates th est, .3 which it may be installed in upright position shown in Fig. 2, or inverted with respect to that view, or on its side.

In operation, but two sets of adjustments are needed, one to move the switch it" by manipulat and the second adjustment by knob t2 for natal-1- ing the frequency with that of the an ennae or other impedance load.

As the drum 20 is rotated for matching the tuning, shoe Z is advanced along its carrying rod and rings T1 and '/2 simply move along shoes 51 and s2 respectively without change in electi'i-- cal connection of the latter.

The device is particularly compact, T'd'd, simple and inexpensive, and serves to attain a complete range of adjustment in frequency range as well as in matching the tank circuit and iim pedance load to any selected frequency.

As many changes could be made in the above construction, and many apparently widely different embodiments of this invention could be made without departing from the scope of the claims, it is intended that all matter contained in the above description or shown in the panying drawings shall be interpreted as illustrative and not in a limiting sense.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

'1. An inductor unit, comprising a frame, an insulating cylindrical drum thereon, an inductor coil about said drum, a plurality of collector rings coaxial with said drum, means aii ixed within said drum electrically connecting each of the rings to a different portion or the coil, contacts on the frame electrically connected to the respective collector rings, a contact shoe engaging the inductor coil, means for connecting an impedance load to said contact shoe and means for adjusting the position of said contact shoe along said cell.

2. An inductor unit, comprising a frame, an insulating drum carried thereby, an inductor coil about said drum and having terminals on said frame, a plurality of collector rings about said drum and spaced from said inductor coil, connectors within. said drum electrically joining the respective collector rings each to a distinct portion of the length of the coil, terminals carried on the frame, means including contact shoes riding on the respective collector rings and electrically connected to said terminals, a contact shoe riding .on said inductor coil, and a terminal on said frame electrically connected to said latter shoe.

3. The combination recited in claim 2 in which the insulating drum is rotatable with its coil and collector rings and the shoes are fixed against movement about the axis of said insulating drum.

4. An inductor unit, comprising a frame including end plates, a hollow cylindrical insulating drum having gudgeons bearing in said end plates, an inductor coil wound upon said drum, the ends of said inductor coil being electrically connected to the respective gudgeons, a plurality of collector rings upon said drum, spaced from said inductor coil, electric connectors extending longitudinally within said hollow drum and connecting said collector rings to associated portions of the length of said coil, metal rods parallel to said drum, mounted in the end plates, contact shoes carried on the respective rods and riding respectively on the various collector rings and upon the inductor coil, each of said rods having a fixed terminal associated with one of the end walls, means for rotating the insulating drum and switch means for selective connection with said fixed terminals for placing the entire inductor coil in circuit or putting into circuit one or more of the collector rings for including in circuit corresponding selected fractions of the inductor coil.

5. An inductor unit, comprising a hollow insulating cylindrical drum, having a helical groove in the outer surface thereof and an inductor coil wire having its convolutions mounted in said groove, a plurality of collector rings comprising wires mounted in corresponding circular grooves on said drum and spaced from said coil, each of said wires having its crown portion protruding from the drum, disks plugging the ends of said drum, each having a gudgeon, connections through the interior of said drum for attaching the respective ends of the inductor coil to the gudgeons, end plates affording bearings for said gudgeons, spacer rods parallel to said drum, and intervening between said plates, metallic crossrods extending between said end plates and parallel to said drum, each having a contact shoe thereon, said shoes riding on and each having a groove straddling the corresponding collector ring wire, each rod having a terminal near the end thereof for connection to the corresponding shoe, and connections in the interior of the drum be-- tween the respective collector rings and fixed points in the coil.

6. An inductor unit, comprising a hollow insulating drum, having a helical groove in the outer surface thereof and an inductor coil having its convolutions mounted in and projecting from said groove, a plurality of collector rings comprising wires mounted in and projecting from corresponding circular grooves on said drum and spaced from said coil, and disks plugging the ends of said drum, each having a gudgeon, connections through the interior of said drum for attaching the respective ends of the inductor coil to the corresponding gudgeons, end plates aifording bearings for said gudgeons, spacer rods parallel to said drum and intervening between said end plates, metal crossrods extending between said end plates and parallel to said drum, each having a contact shoe thereon, each having a groove straddling the corresponding Wire, said shoes riding on the respective collector rings, each rod having a terminal near the end thereof for connection to the corresponding shoe, electrical connections in the interior of the drum between the respective collector rings and fixed points on the coil, a switch plate mounted on the ends of certain of the spacer rods and spaced from one end plate and a switch thereon selectively coacting with the respective collector ring terminals on the associated end plate.

'7. An inductor coil unit, comprising a support frame, a hollow insulating drum having gudgeons mounted in said frame and having an inductor coil thereon, the ends of said coil being electrically connected to said gudgeons, a plurality of wire collector rings on said drum, spaced from said inductor coil, each having an eye at the interior of the drum, radial studs of metal extending through corresponding radial apertures in the drum, each soldered to a coil convolution, and connector wires within the drum each soldered to the corresponding collector ring eye at one end thereof, and to the inner part of the corresponding radial stud at the other end thereof, a hand operated switch mounted on said frame and having a plurality of contacts, metal rods parallel to said drum corresponding to the respective collector rings, each having a contact shoe riding on the associated collector ring, one end of each of said rods being electrically connected to a corresponding one of the switch contacts, means associated with the frame for rotating the drum, a metal rod parallel to said drum affixed in the frame and having a contact shoe riding on the inductor coil, said rod having means adapted for connection of an impedance load thereto.

8. An inductor unit, comprising a pair of end plates, a plurality of spacer rods extending therethrough and forming a frame therewith, an insulating hollow drum having endheads with gudgeons, bearing in said end .plates, one of said end plates having a hand operated transmission thereon for adjustably rotating said drum, the other end plate having a switch plate affixed on spacer rods therethrough, an inductor coil wound upon said drum and having its convolutions in a corresponding helical groove, the ends of said coil extending through the hollow drum and being aflixed to the respective gudgeons, a metal rod parallel to said drum afiixed to said end plates and having a contact shoe riding thereon, said contact shoe having a peripheral groove straddling the inductor wire, stops protruding from the drum beyond the ends of the inductor coil to preclude the shoe from riding oil the respective ends of the wire, a pair of collector rings about the drum spaced from the coil, a pair of metal rods through the end plates, each rod having a contact shoe thereon riding on the corresponding collector ring, said switch plate having switch contacts connected to the respective collector ring contact shoe bearing rods.

SHIRLEY IRVING WEISS.

REFERENCES CITED The following references are of record in the file of this patent: 

